Curved battery-pack devices and accessories

ABSTRACT

A wearable battery-pack accessory may include (1) one or more curved batteries, (2) charging circuitry that charges the one or more curved batteries, (3) supplying circuitry that supplies power to a connected external computing device, and (4) an outer housing including a curved surface shaped to conform to a portion of a wearer&#39;s body. A head-mounted display system may include (1) a head-mounted display, (2) a strap that is coupled to the head-mounted display and wraps around the back of a user&#39;s head when the user is wearing the head-mounted display, and (3) a battery-pack accessory detachably coupled to the strap. Various other apparatus, systems, and methods are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/901,082, filed 16 Sep. 2019, the disclosure of which is incorporated,in its entirety, by this reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate a number of exemplary embodimentsand are a part of the specification. Together with the followingdescription, these drawings demonstrate and explain various principlesof the present disclosure.

FIGS. 1 and 2 are illustrations of an exemplary curved battery cell,according to some embodiments.

FIG. 3 is an illustration of another exemplary curved battery cell,according to some embodiments.

FIGS. 4 and 5 are illustrations of an exemplary curved battery having aspline curvature shaped to conform to a user's head, according to someembodiments.

FIG. 6 is a cross-sectional view of an exemplary curved battery having aspline curvature, according to some embodiments.

FIG. 7 is a perspective view of an exemplary head-mounted display devicein accordance with some embodiments.

FIG. 8 is another perspective view of the exemplary head-mounted displaydevice illustrated in FIG. 7 .

FIG. 9 is a side view of the exemplary head-mounted display deviceillustrated in FIG. 7 .

FIG. 10 is a front view of the exemplary head-mounted display deviceillustrated in FIG. 7 .

FIG. 11 is a rear view of the exemplary head-mounted display deviceillustrated in FIG. 7 .

FIG. 12 is a bottom view of the exemplary head-mounted display deviceillustrated in FIG. 7 .

FIG. 13 is a side view of an exemplary strap assembly for a head-mounteddisplay device in accordance with some embodiments.

FIG. 14 is a perspective view of the strap assembly illustrated in FIG.13 .

FIG. 15 is a top view of the strap assembly illustrated in FIG. 13 .

FIG. 16 is a perspective view of the backpiece illustrated in FIG. 13 .

FIG. 17 is a rear view of the backpiece illustrated in FIG. 13 .

FIG. 18 is a front view of the backpiece illustrated in FIG. 13 .

FIG. 19 is a perspective view of an exemplary battery-pack accessory fora head-mounted display device in accordance with some embodiments.

FIGS. 20 and 21 are perspective views of exemplary components of thebattery-pack accessory illustrated in FIG. 19 .

FIG. 22 is a rear view of the exemplary battery-pack accessoryillustrated in FIG. 19 .

FIG. 23 is a rear view of the exemplary components illustrated in FIGS.20 and 21 .

FIG. 24 is a front view of the exemplary battery-pack accessoryillustrated in FIG. 19 .

FIG. 25 is a front view of the exemplary components illustrated in FIGS.20 and 21 .

FIG. 26 is a top view of the exemplary battery-pack accessoryillustrated in FIG. 19 .

FIG. 27 is a top view of the exemplary components illustrated in FIGS.20 and 21 .

FIG. 28 is another perspective view of the exemplary battery-packaccessory illustrated in FIG. 19 .

FIG. 29 is a perspective view of an exemplary battery-pack accessorymounted to a head-mounted display device in accordance with someembodiments.

FIG. 30 is another perspective view of the exemplary battery-packaccessory and head-mounted display device shown in FIG. 29 .

FIG. 31 is another perspective view of the exemplary battery-packaccessory and head-mounted display device shown in FIG. 29 .

FIG. 32 is a block diagram of an exemplary wearable computing device andcurved battery-pack accessory in accordance with some embodiments.

FIG. 33 is a block diagram of an exemplary wearable computing device andcurved battery-pack accessory in accordance with some embodiments.

FIG. 34 is another block diagram of the exemplary curved battery-packaccessory shown in FIG. 33 in accordance with some embodiments.

FIG. 35 is a front view of a user wearing exemplary curved wearabledevices in accordance with some embodiments.

FIG. 36 is a front view of another user wearing exemplary curvedwearable devices in accordance with some embodiments.

FIG. 37 is a flow diagram of an exemplary method for assembling a curvedbattery-pack accessory.

FIG. 38 is a flow diagram of an exemplary method for manufacturing acurved battery.

FIG. 39 is an illustration of an exemplary step of manufacturing acurved battery in accordance with some embodiments.

FIG. 40 is an illustration of another exemplary step of manufacturing acurved battery in accordance with some embodiments.

FIG. 41 is an illustration of another exemplary step of manufacturing acurved battery in accordance with some embodiments.

FIG. 42 is an illustration of an exemplary curve in accordance with someembodiments.

FIG. 43 is an illustration of another exemplary curve in accordance withsome embodiments.

FIG. 44 is an illustration of another exemplary curve in accordance withsome embodiments.

FIG. 45 is an illustration of an exemplary artificial-reality headbandthat may be used in connection with embodiments of this disclosure.

FIG. 46 is an illustration of exemplary augmented-reality glasses thatmay be used in connection with embodiments of this disclosure.

FIG. 47 is a perspective view of an exemplary head-mounted displaydevice in accordance with some embodiments.

FIG. 48 is an illustration of an exemplary virtual-reality headset thatmay be used in connection with embodiments of this disclosure.

FIG. 49 is an illustration of exemplary haptic devices that may be usedin connection with embodiments of this disclosure.

FIG. 50 is an illustration of an exemplary virtual-reality environmentaccording to embodiments of this disclosure.

FIG. 51 is an illustration of an exemplary augmented-reality environmentaccording to embodiments of this disclosure.

Throughout the drawings, identical reference characters and descriptionsindicate similar, but not necessarily identical, elements. While theexemplary embodiments described herein are susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and will be described in detailherein. However, the exemplary embodiments described herein are notintended to be limited to the particular forms disclosed. Rather, thepresent disclosure covers all modifications, equivalents, andalternatives.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Batteries used in consumer electronic devices, such as lithium-ionbatteries, have traditionally been cylindrical or cuboidal in shape. Formany electronic devices, especially head-mounted and wearable devices,these traditional shapes may lead to constrained battery placement,larger than ideal product size and weight, and/or poor overall productergonomics.

The present disclosure is generally directed to designs for curvedbatteries (e.g., curved battery cells, curved battery modules, and/orcurved battery packs) and various designs and configurations forincorporating curved batteries into wearable devices (e.g., head-mounteddevices or battery-pack accessories). Curved batteries, especiallycurved batteries whose curvatures are modelled using a series of splinesthat approximate the curvatures of one or more users' bodies, may enablewearable devices to be shaped, tuned, and/or customized to better fitindividual users or particular populations of users. Curved batteriesmay be more suitably located within wearable devices, which may enablecurved batteries to be better balanced within the wearable devicesand/or used to counterbalance other elements. For example, ahead-mounted device may incorporate well balanced curved batterieslocated on each side of a user's head. In another embodiment, one ormore curved batteries shaped to conform to the back of a user's head maybe used to counterbalance a head-mounted display located near the frontof the user's head. In some embodiments, a battery pack accessory foruse with a head-mounted display may incorporate one or more curvedbatteries for additional power.

In some embodiments, a battery's curvature may be modelled using aseries of splines (e.g., curves with non-uniform radii) that approximatea complex curvature of one or more users' bodies rather than a singleradius of curvature. Spline curvatures may enable the shape of a batteryto better approximate or conform to the shape of a user's body or head.The curved batteries disclosed herein may include a single cell ormultiple cells (e.g., a single lithium-ion cell or multiple lithium-ioncells). In some embodiments, a curved battery or battery pack mayconsist of (1) a single spline curved cell, (2) multiple cells, whereeach cell has the same or similar spline curve, or (3) multiple cells,where the spline curves differ among at least one of the cells. In someembodiments, the curved batteries disclosed herein may be customized ortuned to a specific person, an average person, or a specific subset ofpeople.

Features from any of the embodiments described herein may be used incombination with one another in accordance with the general principlesdescribed herein. These and other embodiments, features, and advantageswill be more fully understood upon reading the following detaileddescription in conjunction with the accompanying drawings.

The following will provide, with reference to FIGS. 1-6 , detaileddescriptions of example curved batteries. Detailed descriptions ofexample head-mounted display systems that may integrate embodiments ofthese curved batteries will be provided in connection with FIGS. 7-18 .In addition, detailed descriptions of an example curved battery-packaccessory having curved batteries will be provided in connection withFIGS. 19-31 . The descriptions corresponding to FIGS. 32-34 will provideexamples of systems implementing embodiments of the curved battery-packaccessory presented herein. The descriptions corresponding to FIGS. 35and 36 will provide examples of wearable devices that may incorporateembodiments of the curved batteries described herein. The discussionscorresponding to FIGS. 37-41 will provide examples of methods formanufacturing, assembling, configuring, and/or using curved batteriesand curved battery-pack accessories presented herein. The descriptionscorresponding to FIGS. 42-44 will provide examples of non-uniform curvesthat may be used to model the curved batteries presented herein.Finally, with reference to FIGS. 45-51 , the following will providedetailed descriptions of various artificial-reality systems andcomponents that may implement embodiments of the present disclosure.

FIGS. 1 and 2 are illustrations of an exemplary curved battery cell 100,according to some embodiments. As shown, curved battery cell 100 mayhave a curved inner surface 102 and a curved outer surface 104. In atleast one embodiment, surface 102 and surface 104 may be substantiallyparallel to each other. In some embodiments, one or more of curved innersurface 102 and curved outer surface 104 may conform to a curve having auniform or constant radius of curvature. Additionally or alternatively,one or more of curved inner surface 102 and curved outer surface 104 mayconform to a curve having a non-uniform or varying radius of curvature.In some embodiments, surfaces 102 and 104 may have radii of curvature inthe range of 90 mm-120 mm (e.g., 95 mm or 110 mm). In one embodiment,surfaces 102 and 104 may have 95 mm and 100 mm radii, respectively. Inother embodiments, surfaces 102 and 104 may have 110 mm and 115 mmradii, respectively. In some embodiments, curved inner surface 102and/or curved outer surface 104 may be spline surfaces. In someexamples, the term “spline surface” may refer to any curved surface thatmay be modelled or represented using one or more spline curves. In someexamples, the term “spline curve” may refer to an approximating curvethat passes near one or more control points. Additionally oralternatively, the term “spline curve” may refer to an interpolatingcurve that passes through one or more control points. In some examples,the term “spline curve” may refer to a complex or piecewise polynomialcurve constructed from two or more curve segments.

In some examples, curved battery cell 100 may be formed from multipleplanar electrodes (e.g., electrodes 106 and 108) and separators in astacked configuration. As shown, curved battery cell 100 may haveterminals 110 (e.g., a negative terminal 112 and a positive terminal114). Curved battery cell 100 may have any suitable length, width, orthickness and/or may be optimized for a specific use case of curvedbattery cell 100. In some embodiments, curved battery cell 100 may havea length 116 in the range of 60 mm-100 mm or in the range of 70 mm-80mm, a width 118 in the range of 35 mm-45 mm (e.g., approximately 39.50mm), and a thickness in the range of 4-7 mm. In some examples, curvedbattery cell 100 may be a curved lithium-ion cell.

In some embodiments, curved battery cell 100 may be constructed to havea rigid and/or substantially rigid structure from the time ofmanufacture. Alternatively, curved battery cell 100 may be constructedto have a flexible and/or substantially flexible structure. In someembodiments, multiple rigid curved cells may be combined to give acurved battery a flexible and/or substantially flexible structure. Insome embodiments, the multiple rigid curved cells may be connected by aflexible connector (e.g., a hinging connector). By having a non-uniformcurvature, curved battery cell 100 may better conform to a user's body.In some embodiments curved battery cell 100 may have a conformalstructure that matches or approximates the shape of one or more users'heads (e.g., foreheads, backs of heads, etc.).

FIG. 3 is an illustration of exemplary dimensions of an exemplary curvedbattery cell 200, according to some embodiments. As shown, exemplarydimensions of curved battery cell 200 may include a curved length 202, acurved thickness 203, a curved height 204, and an inner radius 206.Curved length 202 may be any suitable length and/or may be optimized fora specific use case of curved battery cell 200. In some examples, curvedlength 202 may be in the range of 60 mm to 100 mm or in the range of 70mm to 80 mm (e.g., approximately 74.48 mm). Curved thickness 203 may beany suitable thickness and/or may be optimized for a specific use caseof curved battery cell 200. In some examples, thickness 203 may be inthe range of 4-7 mm (e.g., approximately 5.50 mm). Curved height 204 maybe any suitable height and/or may be optimized for a specific use caseof curved battery cell 200. In some examples, curved height 204 may bein the range of 10 mm to 18 mm (e.g., approximately 14.00 mm). Innerradius 206 may be any suitable radius and/or may be optimized for aspecific use case of curved battery cell 200. In some examples, curvedbattery cell 200 may form all or part of a head-mounted battery and beoptimally sized to conform to one or more users' heads or an averagehuman head. In one such example, inner radius 206 may optimally bebetween approximately 80 mm and 95 mm. In another such example, innerradius 206 may optimally be between approximately 70 mm and 125 mm. Insome examples, inner radius 206 may be approximately 95 mm (e.g., 95mm+/−5 mm) or approximately 110 mm (e.g., 110 mm+/−5 mm).

In some embodiments, the disclosed curved batteries may have fixed,constant, or uniform radii of curvature. Additionally or alternatively,the disclosed curved batteries may have varying, non-fixed, ornon-uniform radii of curvature. FIGS. 4 and 5 are illustrations of anexemplary curved battery 300 having non-uniform radii of curvature. Inthe example shown, curved battery 300 is shaped to conform to thecurvatures and contours of a head 302 (illustrated having contour lines304). Head 302 may represent a measured or scanned head of a singleperson or a head whose contours are derived by averaging the headcontours of a particular group of people. For example, head 302 mayrepresent the head of an average 10, 15, or 21 year old person. Whilebattery 300 is illustrated as conforming to the side of head 302, thecurved batteries described herein may be manufactured to conform to anyother part of head 302 or any other body part and/or manufactured toapproximate the curvatures of any of contour lines 304. In someembodiments, the curvature of battery 300 may be selected to conform,within a margin or a degree of comfort, to the heads or bodies ofcertain population or groups (e.g., the 95th percentile of the largestmeasured male head to the 5th percentile of the smallest measured femalehead).

In some embodiments, the curvatures of one or more surfaces of battery300 and/or the curvatures of battery 300 as a whole may be modelledusing a series of splines. In some embodiments, the term “spline” mayrefer to a non-simple curve, a non-uniform curve, a complex curve, acurve with a non-continuous radius or circumradius, a piecewisepolynomial curve, or any curve without a single fixed radius orcircumradius. In some embodiments, the batteries disclosed herein may beproduced using a single cell or multiple cells. For example, battery 300may consist of (1) a single cell, with a spline curved cell, (2)multiple cells, where each cell has the same or similar spline curve, or(3) multiple cells, where the spline curves differ among at least one ofthe cells. Batteries having spline-based curvatures may enable betterdesigns for wearable devices, such as head-mounted display devices. Insome instances, head-mounted display devices with integrated curvedbatteries may have improved ergonomics which may reduce neck strainand/or other types of fatigue. In some embodiments, the curvedbatteries, devices, and accessories disclosed herein may be personalizedto fit a particular person, much like prescription glasses arepersonalized.

FIG. 6 is an illustration of an exemplary spline battery 500, accordingto some embodiments. As shown, spline battery 500 may have a spline-fitsurface 502 and a spline-fit surface 504. In some embodiments, thespline curvatures of surfaces 502 and 504 may have radii in the range of90 mm-120 mm. In some examples, spline battery 500 may be formed frommultiple planar electrodes (e.g., electrodes 506 and 508) and separatorsin a stacked configuration. As shown in FIG. 5 , spline battery 500 mayhave multiple curved regions (region 510 and region 512), each withuniform or non-uniform curvatures.

The batteries disclosed herein may generally have curvatures with radiisuitable to conform to portions of a wearer's body or suitable to beintegrated into wearable devices and/or accessories that conform toportions of a wearer's body. In some embodiments, the batteriesdisclosed herein may have curvatures with radii within the range of 90mm-120 mm, 70 mm-110 mm, 85 mm-110 mm, 76 mm-84 mm, 72 mm-88 mm, 68mm-92 mm, 64 mm-96 mm, 80.75 mm-89.25 mm, 76.5 mm-93.5 mm, 72.25mm-97.75 mm, 68 mm-102 mm, 85.5 mm-94.5 mm, 81 mm-99 mm, 76.5 mm-103.5mm, 72 mm-108 mm, 90.25 mm-99.75 mm, 85.5 mm-104.5 mm, 80.75 mm-109.25mm, 76 mm-114 mm, 95 mm-105 mm, 90 mm-110 mm, 85 mm-115 mm, 80 mm-120mm, 99.75 mm-110.25 mm, 94.5 mm-115.5 mm, 89.25 mm-120.75 mm, 84 mm-126mm, 104.5 mm-115.5 mm, 99 mm-121 mm, 93.5 mm-126.5 mm, 88 mm-132 mm,85.5 mm-104.5 mm, 76 mm-114 mm, 66.5 mm-123.5 mm, 57 mm-133 mm, 47.5mm-142.5 mm, 38 mm-152 mm, 28.5 mm-161.5 mm, 19 mm-171 mm, or 9.5mm-180.5 mm. In some embodiments, the batteries disclosed herein mayhave single curvatures with radii that range between 90 mm and 120 mm,70 mm and 110 mm, 85 mm and 110 mm, 76 mm and 84 mm, 72 mm and 88 mm, 68mm and 92 mm, 64 mm and 96 mm, 80.75 mm and 89.25 mm, 76.5 mm and 93.5mm, 72.25 mm and 97.75 mm, 68 mm and 102 mm, 85.5 mm and 94.5 mm, 81 mmand 99 mm, 76.5 mm and 103.5 mm, 72 mm and 108 mm, 90.25 mm and 99.75mm, 85.5 mm and 104.5 mm, 80.75 mm and 109.25 mm, 76 mm and 114 mm, 95mm and 105 mm, 90 mm and 110 mm, 85 mm and 115 mm, 80 mm and 120 mm,99.75 mm and 110.25 mm, 94.5 mm and 115.5 mm, 89.25 mm and 120.75 mm, 84mm and 126 mm, 104.5 mm and 115.5 mm, 99 mm and 121 mm, 93.5 mm and126.5 mm, 88 mm and 132 mm, 85.5 mm and 104.5 mm, 76 mm and 114 mm, 66.5mm and 123.5 mm, 57 mm and 133 mm, 47.5 mm and 142.5 mm, 38 mm and 152mm, 28.5 mm and 161.5 mm, 19 mm and 171 mm, or 9.5 mm and 180.5 mm.

FIGS. 7-12 illustrate an exemplary head-mounted-display system 600 inaccordance with some embodiments. While the components illustrated inthese figures are not illustrated as incorporating the curved batteriesdisclosed herein, any of the curved components of head-mounted-displaysystem 600 may include or integrate curved batteries. Similarly, any ofthe devices or components disclosed herein may similarly include orintegrate curved batteries. Head-mounted display system 600 includes ahead-mounted display device 602 (e.g., a head-mounted display), audiosubsystems 604, a strap assembly 606, and a facial-interface subsystem608. In some embodiments, the term “head-mounted display” may refer toany type or form of display device or system that is worn on or about auser's head and displays visual content to a user. Head-mounted displaysmay display content in any suitable manner, including via a screen(e.g., an LCD or LED screen), a projector, a cathode ray tube, anoptical mixer, etc. Head-mounted displays may display content in one ormore of various media formats. For example, a head-mounted display maydisplay video, photos, and/or computer-generated imagery (CGI).

Head-mounted displays may provide diverse and distinctive userexperiences. Some head-mounted displays may provide virtual-realityexperiences (i.e., they may display computer-generated or pre-recordedcontent), while other head-mounted displays may provide real-worldexperiences (i.e., they may display live imagery from the physicalworld). Head-mounted displays may also provide any mixture of live andvirtual content. For example, virtual content may be projected onto thephysical world (e.g., via optical or video see-through), which mayresult in augmented reality or mixed reality experiences.

In some embodiments, head-mounted display device 602 may include anouter housing 610 that may surround, contain, and protect variousdisplay, optical, and other electronic components of head-mounteddisplay device 602. As shown, head-mounted display device 602 mayinclude one or more optical sensors 612 (such as two-dimensional (2D) or3D cameras, time-of-flight depth sensors, single-beam or sweeping laserrangefinders, 3D LiDAR sensors, and/or any other suitable type or formof optical sensor), ports 613 (e.g., an audio port, a power port, a dataport, or a Universal Serial Bus (USB) port), and/or a volume rockerbutton 630. Outer housing 610 may be attached to strap assembly 606 byany suitable interfaces. Facial-interface subsystem 608 may beconfigured to comfortably rest against a region of a user's face,including a region surrounding the user's eyes, when head-mounteddisplay system 600 is worn by the user. In these embodiments,facial-interface subsystem 608 may include a facial-interface cushion614. Facial-interface cushion 614 may surround a viewing region 616 thatincludes the user's field of vision while the user is wearinghead-mounted display system 600.

In some embodiments, strap assembly 606 may be used to mounthead-mounted display device 602 on a user's head. As shown in FIG. 7 ,strap assembly 606 may include an upper strap 618 and lower straps 620.Lower straps 620 may each be coupled to one of audio subsystems 604,which are shown coupled to head-mounted display device 602. In someembodiments, upper strap 618 and lower straps 620 may be formed from asoft and/or flexible material that enable upper strap 618 and lowerstraps 620 to adjustably conform to the top and/or sides of a user'shead when the user is wearing head-mounted display device 602. In thisexample, strap assembly 606 may include strap retaining components 624,626, and 628 that may couple upper strap 618 and lower straps 620 andenable them to be adjusted. In some embodiments, strap assembly 606 mayinclude curved batteries and/or various electronic components that maygenerate and/or display data.

FIGS. 13-18 illustrate an exemplary strap assembly 1200. While thecomponents illustrated in these figures are not illustrated asincorporating the curved batteries disclosed herein, any of the curvedcomponents of exemplary strap assembly 1200 may include or integratecurved batteries. In some examples, strap assembly 1200 may replacestrap assembly 606 and may be used to mount head-mounted display device602 on a user's head. As shown in FIGS. 13-18 , strap assembly 1200 mayinclude a left strap 1202, a right strap 1204, and a backpiece 1206(including a cushion 1212) to rest against the back of the user's head(e.g., around the user's occipital lobe). In some embodiments, leftstrap 1202 and right strap 1204 may include interfaces (e.g., snapinterface 1214) that couple left strap 1202 and right strap 1204 to oneof audio subsystems 604. In some embodiments, left strap 1202 and rightstrap 1204 may be formed from a rigid or semi-rigid material that enableleft strap 1202 and right strap 1204 to adjustably conform to the sidesof a user's head when the user is wearing head-mounted display device602. As shown, strap assembly 1200 may include a dial 1210 for adjustingand/or locking the positions of left strap 1202 and right strap 1204. Insome embodiments, dial 1210 may be used to interface with a strapadjustment assembly contained within a strap housing 1208. As shown inFIG. 16 , strap housing 1208 may include surfaces 1216.

In some embodiments, a curved battery-pack accessory that includes oneor more of the curved batteries disclosed herein may be attached tostrap assembly 606 or strap assembly 1200 to provide primary orauxiliary power to head-mounted display device 602. FIGS. 19-31illustrate an exemplary removable curved battery-pack accessory 1800 fora head-mounted-display system (e.g., head-mounted-display system 600).In some examples, battery-pack accessory 1800 may be configured to beworn near or against the back of a user's head and/or act as acounterweight that counterbalances other components of a head-mounteddisplay system worn near or against the user's face (e.g., head-mounteddisplay device 602). As shown in FIGS. 29-31 , battery-pack accessory1800 may be shaped and configured to attach to backpiece 1206 of strapassembly 1200. In the example shown, battery-pack accessory 1800 may beshaped and configured to surround and attach to strap housing 1208 via afriction or snap fit.

As shown in FIG. 19 , removable battery-pack accessory 1800 may includea curved back element 1802 and a curved front element 1804 that houseand surround a curved battery assembly 1900 shown in FIG. 20 . In someexamples, curved front element 1804 may be sized to interface with straphousing 1208 of backpiece 1206. As shown in FIGS. 19 and 28 , curvedfront element 1804 may include a notch or opening 1806 and/or a notch oropening 2702 for exposing dial 1210 when attached to backpiece 1206(e.g., as illustrated in FIGS. 29-31 ).

In the example shown in FIG. 20 , battery assembly 1900 may include aleft curved battery 1902, a right curved battery 1904, a printed circuitboard 1906, ribbon cables 1908 and 1910, and at least one connector1912. In some embodiments, curved batteries 1902 and or 1904 may beconfigured similar to curved battery cell 100, curved battery cell 200,or curved battery 300. In alternative embodiments, curved battery-packaccessory 1800 may include a single curved battery or more than twocurved batteries.

In some embodiments, battery assembly 1900 may provide primary orauxiliary power to head-mounted display device 602. As shown in FIG. 29, removable battery-pack accessory 1800 may transmit power and/or otherdata to head-mounted display device 602 via a cable 2802. In someembodiments, battery assembly 1900 may receive power via one connector(e.g., connector 1912) and transmit power via another. In otherembodiments, battery assembly 1900 may receive and transmit power via asingle connector. In some embodiments, battery assembly 1900 may act asa power conduit that relays power to head-mounted display device 602. Insome embodiments, printed circuit board 1906 may include circuitryconfigured to charge batteries 1902 and 1904 and/or relay power frombatteries 1902 and 1904 to a connected head-mounted display system. Insome embodiments, printed circuit board 1906 may represent a protectioncontrol module or a protection circuit module.

Removable battery-pack accessory 1800 may be attached to backpiece 1206in any suitable manner. In one embodiment, removable battery-packaccessory 1800 may include an inner surface 2704 that is sized for afriction fit with surfaces 1216. Additionally or alternatively,removable battery-pack accessory 1800 may include ridges 2706 that aresized for a snap fit with surfaces 1216.

FIG. 32 shows an exemplary system 3200 consisting of a wearablecomputing device 3202 (e.g., head-mounted display 602), a power supply3204 (e.g., an Alternating Current (AC) power source or a Direct Current(DC) power source), and a curved battery-pack accessory 3206 (e.g.,curved battery-pack accessory 1800). As shown, wearable computing device3202 may include one or more electronic components 3208, a powermanagement subsystem 3210 for supplying power to electronic components3208, one or more curved batteries 3212 for supplying power to powermanagement subsystem 3210, and a power port 3214 for connecting toexternal power sources (e.g., power supply 3204 or curved battery-packaccessory 3206). Curved battery-pack accessory 3206 may include one ormore curved batteries 3220, a battery management subsystem 3218 forsupplying power to or extracting power from curved batteries 3220, andpower ports 3216 (e.g., an input port 3217 for receiving power from anexternal power source and an output port 3215 for supplying power to anexternal device).

In the configuration shown in FIG. 32 , power supply 3204 may bedetachably connected to curved battery-pack accessory 3206 by a powercable 3203 at input port 3217, and wearable computing device 3202 may bedetachably connected to curved battery-pack accessory 3206 by a powercable 3205 at power port 3214 and output port 3215. In thisconfiguration, curved battery-pack accessory 3206 may relay power frompower supply 3204 to wearable computing device 3202 while also chargingcurved batteries 3220. In an alternative configuration, power supply3204 may be detached from curved battery-pack accessory 3206. In thisconfiguration, curved battery-pack accessory 3206 may supply power fromcurved batteries 3220 to wearable computing device 3202. In anotheralternative configuration, power supply 3204 may be attached to curvedbattery-pack accessory 3206 while wearable computing device 3202 isdetached from curved battery-pack accessory 3206. In this configuration,curved battery-pack accessory 3206 may charge curved batteries 3220without supplying power to any external device.

FIG. 33 shows an exemplary system 3300 consisting of a wearablecomputing device 3302 (e.g., head-mounted display 602), a power supply3304 (e.g., an Alternating Current (AC) power source or a Direct Current(DC) power source), and a curved battery-pack accessory 3306 (e.g.,curved battery-pack accessory 1800). As shown, wearable computing device3302 may include one or more electronic components 3308, a powermanagement subsystem 3310 for supplying power to electronic components3308, one or more curved batteries 3312 for supplying power to powermanagement subsystem 3310, and a power port 3314 for connecting toexternal power sources (e.g., power supply 3304 or curved battery-packaccessory 3306). Curved battery-pack 3306 may include one or more curvedbatteries 3320, a battery management subsystem 3318 for supplying powerto or extracting power from curved batteries 3320, and a power port 3316for receiving power from an external power source and for supplyingpower to an external device.

In the configuration shown in FIG. 33 , power port 3314 of wearablecomputing device 3302 may be detachably connected to power port 3316 ofcurved battery-pack accessory 3306. In this configuration, curvedbattery-pack accessory 3306 may supply power from curved batteries 3320to wearable computing device 3302. In the configuration shown in FIG. 34, power supply 3304 may be detachably connected to curved battery-packaccessory 3306 by power carrying cable 3305 at power port 3316. In thisconfiguration, curved battery-pack accessory 3306 may use power frompower supply 3304 to charge curved batteries 3320.

The curved batteries and curved battery-pack accessories disclosedherein may be implemented into, conformed to, and/or suitably shaped tofit within a variety of wearable devices. For example, all or a portionof example systems 3200 or 3300 may represent portions of examplesystems 3500 and 3600 shown in FIGS. 35 and 36 . As shown in FIG. 35 ,system 3500 may include a user 3502 and various power-consuming andpower-supplying devices that are worn or held by user 3502. For example,FIG. 35 illustrates a head-mounted display system 3504, such ashead-mounted display system 600, worn on the head of user 3502, a smartwatch 3506 worn on a wrist of user 3502, and a smart phone 3508 held ina hand of user 3502. As shown in FIG. 36 , system 3600 may include auser 3602 and various power-consuming and power-supplying devices thatare worn or held by user 3602. For example, FIG. 36 illustrates ahead-mounted display device 3604, such as head-mounted display device4700 illustrated in FIG. 47 , worn on the head of user 3602, anelectronic device 3606 worn on a wrist of user 3602, an electronicdevice 3608 worn about neck region of user 3602, an electronic device3610 worn on an ankle of user 3602, and a flexible electronic device3612 worn on a forearm of user 3602. In some examples, one or more ofthe devices shown in FIGS. 35 and 36 may be shaped to conform to acorresponding portion of the wearers' bodies, and the curved batteriescontained therein may be similarly shaped to conform to thecorresponding portion of the wearers' bodies.

FIG. 37 is a flow diagram of an exemplary assembly method 3700 forassembling a curved battery-pack accessory according to any of theembodiments disclosed herein. The steps shown in FIG. 37 may beperformed by an individual and/or by any suitable manual and/orautomated apparatus. As illustrated in FIG. 37 , at step 3710, a curvedbattery cell shaped to fit within the curved battery-pack accessory maybe provided. In some examples, the curved battery cell may be shaped tominimize the size of the curved battery-pack accessory. At step 3720,the curved battery cell may be coupled to charging circuitry configuredto charge the curved battery within the curved battery-pack accessory.At step 3730, the curved battery cell may be coupled to supplyingcircuitry configured to supply power to an external wearable computingdevice. At step 3740, the curved battery cell may be placed within anouter housing having a curved surface shaped to conform to a portion ofa wearer's body.

FIG. 38 is a flow diagram of an exemplary manufacturing method 3800 forforming curved battery cells according to any of the embodimentsdisclosed herein. The steps shown in FIG. 38 may be performed by anindividual and/or by any suitable manual and/or automated apparatus. Asillustrated in FIG. 38 , at step 3810, a flat electrode assembly may beplaced between spline surfaces of an upper jig and a lower jig of amolding or punching tool. Using FIG. 39 as an example, a flat cuboidalelectrode assembly 3900 may be placed between an upper jig 3902 and alower jig 3904. As shown in FIG. 39 , upper jig 3902 and lower jig 3904may have matching spline surfaces 3903 and 3905. In some embodiments,the spline surfaces of upper jig 3902 and/or lower jig 3904 may bemachined or otherwise shaped to substantially match the curvatures ofone or more users' bodies (e.g., faces, heads, wrists, etc.).

At step 3820 in FIG. 38 , the flat electrode assembly may be curved bypressing the flat electrode assembly between the spline surfaces of theupper jig and the lower jig. Using FIGS. 39 and 40 as examples, flatcuboidal electrode assembly 3900 may be turned into curved electrodeassembly 4000 by pressing flat cuboidal electrode assembly 3900 betweenupper jig 3902 and lower jig 3904. In some examples, the upper jig andthe lower jig may be heated before or while pressing the flat electrodeassembly. In some examples, pressing step 3820 may be repeated multipletimes to get the final shape needed.

At step 3830 in FIG. 38 , the upper jig may be separated from the lowerjig to reveal the curved electrode assembly. Then at step 3840, thecurved electrode assembly may be removed from the upper jig and thelower jig. Using FIG. 40 as an example, upper jig 3902 may be separatedfrom lower jig 3904 to reveal curved electrode assembly 4000. Afterremoval, a curved electrode assembly may be placed in a cell case orpackaging. An electrolyte may also be added to the cell case orpackaging, and a charging formation process may be initiated. Finally,the curved electrode assembly may be incorporated into a wearable device(e.g., a head-mounted device) or a curved battery pack. In someembodiments, the curved electrode assembly may be combined withadditional curved electrode assemblies to form a curved battery pack. Insome embodiments, the curved electrode assembly and the additionalcurved electrode assemblies may have substantially similar curvatures.Alternatively, the curved electrode assembly and the additional curvedelectrode assemblies may have different curvatures.

The curved batteries and curved battery-pack accessories describedherein may be modeled by or shaped to conform to any suitable simple orcomplex curve. For example, the curved batteries and curved battery-packaccessories described herein may be modeled by or shaped to conform toall or a portion of one of the exemplary curves illustrated in FIGS.42-44 . FIG. 42 illustrates an exemplary non-uniform curve 4200 having astarting point 4202 and an ending point 4204. In this example, theradius of curvature of non-uniform curve 4200 may range from a radius4206 at point 4202 to a radius 4208 midway between starting point 4202and ending point 4204 to a radius 4210 at ending point 4204. As shown,radius 4206, radius 4208, and radius 4210 may all be different radii.FIG. 43 illustrates a non-uniform curve 4300 having multiple curvesegments 4302, 4304, and 4306. In some examples, the systems disclosedherein may represent one or more of curve segments 4302-4306 using apolynomial function. As shown, curve segment 4302 may begin at point4308 and end at point 4310, curve segment 4304 may begin at point 4310and end at point 4312, and curve segment 4306 may begin at point 4312and end at point 4314. In this example, curve segment 4302 may have acontinuously varying radius of curvature, curve segment 4304 may have aconstant radius of curvature (i.e., equal to radius 4316 of circle4318), and curve segment 4306 may have a continuously varying radius ofcurvature. FIG. 44 illustrates an exemplary spline 4402 formed bymultiple control points (e.g., control points 4404, 4406, 4408, 4410,4412, and 4414). In some examples, spline 4402 may represent anapproximating curve and may pass near one or more of control points4404-4414.

Example Embodiments

Example 1: A wearable battery-pack accessory including (1) one or morecurved batteries, (2) charging circuitry that charges the one or morecurved batteries, (3) supplying circuitry that supplies power to aconnected external computing device, and (4) an outer housing includinga curved surface shaped to conform to a portion of a wearer's body.

Example 2: The wearable battery-pack accessory of Example 1, wherein theconnected external computing device is a head-mounted display system.

Example 3: The wearable battery-pack accessory of any of Examples 1 and2 further including an interface for coupling the wearable battery-packaccessory to a strap assembly of the head-mounted display system.

Example 4: The wearable battery-pack accessory of any of Examples 1-3,wherein the one or more curved batteries include (1) a top batterycurved to conform to a top side of the wearer's head, (2) a rightbattery curved to conform to a right side of the wearer's head, or (3) aleft battery curved to conform to a left side of the wearer's head.

Example 5: The wearable battery-pack accessory of any of Examples 1-4,wherein the one or more curved batteries include a single battery curvedto conform to a back side of the wearer's head and extend from a rightside of the wearer's head to a left side of the wearer's head.

Example 6: The wearable battery-pack accessory of any of Examples 1-5,wherein the curved surface of the outer housing has a non-uniform radiusof curvature that approximates a curvature of the portion of thewearer's body.

Example 7: The wearable battery-pack accessory of any of Examples 1-6,wherein each of the one or more curved batteries has an inner radiusbetween 80 millimeters and 95 millimeters.

Example 8: The wearable battery-pack accessory of any of Examples 1-7,wherein each of the one or more curved batteries has an inner radiusbetween 70 millimeters and 125 millimeters.

Example 9: The wearable battery-pack accessory of any of Examples 1-8,further including (1) an input port for receiving power from an externalpower source and (2) an output port for transmitting power to theconnected external computing device, wherein the charging circuitrycharges the one or more curved batteries using power from the externalpower source while the supplying circuitry supplies power to theconnected external computing device.

Example 10: The wearable battery-pack accessory of any of Examples 1-9,further including an input/output port for receiving power from anexternal power source and transmitting power to the connected externalcomputing device, wherein the charging circuitry charges the one or morecurved batteries when the external power source is connected to theinput/output port and the supplying circuitry supplies power to theconnected external computing device when the connected externalcomputing device is connected to the input/output port.

Example 11: A head-mounted display system including (1) a head-mounteddisplay, (2) a strap that is coupled to the head-mounted display andwraps around the back of a user's head when the user is wearing thehead-mounted display, and (3) a battery-pack accessory detachablycoupled to the strap, the battery-pack accessory including (a) one ormore curved batteries, (b) charging circuitry that charges the one ormore curved batteries, (c) supplying circuitry that supplies power tothe head-mounted display, and (d) an outer housing including a curvedsurface shaped to conform to a portion of the user's head.

Example 12: The head-mounted display system of Example 11, wherein thestrap includes an adjustment mechanism for adjusting a size of thestrap, the adjustment mechanism includes a dial, and the outer housingof the battery-pack accessory includes a notch that exposes the dialwhen the battery-pack accessory is coupled to the strap.

Example 13: The head-mounted display system of any of Examples 11-12,wherein the outer housing of the battery-pack accessory includes aninterface for coupling the battery-pack accessory, via a friction fit,to the strap of the head-mounted display system.

Example 14: The head-mounted display system of any of Examples 11-13,wherein the one or more curved batteries include (1) a top batterycurved to conform to a top side of the wearer's head, (2) a rightbattery curved to conform to a right side of the user's head, or (3) aleft battery curved to conform to a left side of the user's head.

Example 15: The head-mounted display system of any of Examples 11-14,wherein the one or more curved batteries include a single battery curvedto conform to a back side of the user's head and extend from a rightside of the user's head to a left side of the user's head.

Example 16: The head-mounted display system of any of Examples 11-15,wherein each of the one or more curved batteries has an inner radiusbetween 80 millimeters and 95 millimeters.

Example 17: The head-mounted display system of any of Examples 11-16,wherein each of the one or more curved batteries has an inner radiusbetween 70 millimeters and 125 millimeters.

Example 18: The head-mounted display system of any of Examples 11-17,wherein the battery-pack accessory further includes (1) an input portfor receiving power from an external power source and (2) an output portfor transmitting power to the head-mounted display, wherein the chargingcircuitry charges the one or more curved batteries using power from theexternal power source while the supplying circuitry supplies power tothe head-mounted display.

Example 19: The head-mounted display system of any of Examples 11-18,further including an input/output port for receiving power from anexternal power source and transmitting power to the head-mounteddisplay, wherein the charging circuitry charges the one or more curvedbatteries when the external power source is connected to theinput/output port and the supplying circuitry supplies power to thehead-mounted display when the head-mounted display is connected to theinput/output port.

Example 20: A method including (1) providing a curved battery, (2)coupling the curved battery to charging circuitry that charges thecurved battery, (3) coupling the curved battery to supplying circuitrythat supplies power to an external computing device; and (4) placing thecurved battery, the charging circuitry, and the supplying circuitrywithin an outer housing comprising a curved surface shaped to conform toa portion of a wearer's body.

Additional Example Embodiments

Example 21: A curved battery cell including (1) a positive terminal, (2)a negative terminal, (3) one or more curved electrodes, and (4) an outercase encasing the one or more curved electrodes, wherein the outer caseincludes at least one curved surface having a non-uniform radius ofcurvature.

Example 22: The curved battery cell of Example 21, wherein the curvedsurface is a spline surface.

Example 23: The curved battery cell of any of Examples 21-22, whereinthe curved surface is shaped to conform to one or more users' bodies.

Example 24: The curved battery cell of any of Examples 21-23, whereinthe curved surface is shaped to conform to one or more users' heads.

Example 25: The curved battery cell of any of Examples 21-24, whereinthe curved surface is shaped to conform to one side of the back of oneor more users' heads.

Example 26: The curved battery cell of any of Examples 21-25, whereinthe curved surface is shaped to conform to a portion of a strap of ahead-mounted display system when the head-mounted display system is wornand the portion of the strap conforms to a user's head.

Example 27: The curved battery cell of any of Examples 21-26, whereinthe curved surface includes at least a first area and a second area, thefirst area has a first radius of curvature, the second area has a secondradius of curvature, and the first radius of curvature and the secondradius of curvature are different.

Example 28: The curved battery cell of any of Examples 21-27, whereinthe curved surface includes at least a first area and a second area, thefirst area has a constant radius of curvature, and the second area has avarying radius of curvature.

Example 29: The curved battery cell of any of Examples 21-28, whereinthe curved surface is an inner surface of the outer case having anon-uniform inner radius within a range of 80 millimeters and 95millimeters.

Example 30: The curved battery cell of any of Examples 21-29, whereinthe curved surface is an inner surface of the outer case having anon-uniform inner radius within a range of 70 millimeters and 125millimeters.

Example 31: A curved battery pack including (1) a first curved batterycell having a first outer surface, wherein the first outer surface has afirst non-uniform curvature and (2) a second curved battery cell havinga second outer surface, wherein the second outer surface has a secondnon-uniform curvature.

Example 32: The curved battery pack of Example 31, wherein the firstouter surface and the second outer surface are spline surfaces.

Example 33: The curved battery pack of any of Examples 31-32, whereinthe first non-uniform curvature and the second non-uniform curvature areequal.

Example 34: The curved battery pack of any of Examples 31-33, whereinthe first non-uniform curvature and the second non-uniform curvature aremirrored.

Example 35: The curved battery pack of any of Examples 31-34, whereinthe first non-uniform curvature and the second non-uniform curvature arespline curvatures.

Example 36: The curved battery pack of any of Examples 31-35, whereinthe first outer surface and the second outer surface are shaped toconform to one or more users' bodies.

Example 37: The curved battery pack of any of Examples 31-36 furtherincluding a bendable joining member coupling the first curved batterycell to the second curved battery cell.

Example 38: A method including (1) placing a flat electrode assemblybetween matching spline surfaces of an upper jig and a lower jig, (2)curving the flat electrode assembly by pressing the flat electrodeassembly between the spline surfaces of the upper jig and the lower jig,(3) separating the upper jig from the lower jig, and (4) removing thecurved electrode assembly from the upper jig and the lower jig.

Example 39: The method of Example 38 further including heating the upperjig and the lower jig.

Example 40: The method of any of Examples 38-39, wherein the flatelectrode assembly includes a plurality of stacked electrodes.

Embodiments of the present disclosure may include or be implemented inconjunction with various types of artificial-reality systems. Artificialreality is a form of reality that has been adjusted in some mannerbefore presentation to a user, which may include, for example, a virtualreality, an augmented reality, a mixed reality, a hybrid reality, orsome combination and/or derivative thereof. Artificial-reality contentmay include completely computer-generated content or computer-generatedcontent combined with captured (e.g., real-world) content. Theartificial-reality content may include video, audio, haptic feedback, orsome combination thereof, any of which may be presented in a singlechannel or in multiple channels (such as stereo video that produces athree-dimensional (3D) effect to the viewer). Additionally, in someembodiments, artificial reality may also be associated withapplications, products, accessories, services, or some combinationthereof, that are used to, for example, create content in an artificialreality and/or are otherwise used in (e.g., to perform activities in) anartificial reality.

Artificial-reality systems may be implemented in a variety of differentform factors and configurations. Some artificial-reality systems may bedesigned to work without near-eye displays (NEDs), an example of whichis augmented-reality system 4500 in FIG. 45 . Other artificial-realitysystems may include an NED that also provides visibility into the realworld (e.g., augmented-reality system 4600 in FIG. 46 ) or that visuallyimmerses a user in an artificial reality (e.g., virtual-reality system4800 in FIG. 48 ). While some artificial-reality devices may beself-contained systems, other artificial-reality devices may communicateand/or coordinate with external devices to provide an artificial-realityexperience to a user. Examples of such external devices include handheldcontrollers, mobile devices, desktop computers, devices worn by a user,devices worn by one or more other users, and/or any other suitableexternal system.

Turning to FIG. 45 , augmented-reality system 4500 generally representsa wearable device dimensioned to fit about a body part (e.g., a head) ofa user. As shown in FIG. 45 , system 4500 may include a frame 4502 and acamera assembly 4504 that is coupled to frame 4502 and configured togather information about a local environment by observing the localenvironment. Augmented-reality system 4500 may also include one or moreaudio devices, such as output audio transducers 4508(A) and 4508(B) andinput audio transducers 4510. Output audio transducers 4508(A) and4508(B) may provide audio feedback and/or content to a user, and inputaudio transducers 4510 may capture audio in a user's environment.

As shown, augmented-reality system 4500 may not necessarily include anNED positioned in front of a user's eyes. Augmented-reality systemswithout NEDs may take a variety of forms, such as head bands, hats, hairbands, belts, watches, wrist bands, ankle bands, rings, neckbands,necklaces, chest bands, eyewear frames, and/or any other suitable typeor form of apparatus. While augmented-reality system 4500 may notinclude an NED, augmented-reality system 4500 may include other types ofscreens or visual feedback devices (e.g., a display screen integratedinto a side of frame 4502).

The embodiments discussed in this disclosure may also be implemented inaugmented-reality systems that include one or more NEDs. For example, asshown in FIG. 46 , augmented-reality system 4600 may include an eyeweardevice 4602 with a frame 4610 configured to hold a left display device4615(A) and a right display device 4615(B) in front of a user's eyes.Display devices 4615(A) and 4615(B) may act together or independently topresent an image or series of images to a user. While augmented-realitysystem 4600 includes two displays, embodiments of this disclosure may beimplemented in augmented-reality systems with a single NED or more thantwo NEDs.

In some embodiments, augmented-reality system 4600 may include one ormore sensors, such as sensor 4640. Sensor 4640 may generate measurementsignals in response to motion of augmented-reality system 4600 and maybe located on substantially any portion of frame 4610. Sensor 4640 mayrepresent a position sensor, an inertial measurement unit (IMU), a depthcamera assembly, or any combination thereof. In some embodiments,augmented-reality system 4600 may or may not include sensor 4640 or mayinclude more than one sensor. In embodiments in which sensor 4640includes an IMU, the IMU may generate calibration data based onmeasurement signals from sensor 4640. Examples of sensor 4640 mayinclude, without limitation, accelerometers, gyroscopes, magnetometers,other suitable types of sensors that detect motion, sensors used forerror correction of the IMU, or some combination thereof.Augmented-reality system 4600 may also include a microphone array with aplurality of acoustic transducers 4620(A)-4620(J), referred tocollectively as acoustic transducers 4620. Acoustic transducers 4620 maybe transducers that detect air pressure variations induced by soundwaves. Each acoustic transducer 4620 may be configured to detect soundand convert the detected sound into an electronic format (e.g., ananalog or digital format). The microphone array in FIG. 2 may include,for example, ten acoustic transducers: 4620(A) and 4620(B), which may bedesigned to be placed inside a corresponding ear of the user, acoustictransducers 4620(C), 4620(D), 4620(E), 4620(F), 4620(G), and 4620(H),which may be positioned at various locations on frame 4610, and/oracoustic transducers 4620(I) and 4620(J), which may be positioned on acorresponding neckband 4605.

In some embodiments, one or more of acoustic transducers 4620(A)-(F) maybe used as output transducers (e.g., speakers). For example, acoustictransducers 4620(A) and/or 4620(B) may be earbuds or any other suitabletype of headphone or speaker.

The configuration of acoustic transducers 4620 of the microphone arraymay vary. While augmented-reality system 4600 is shown in FIG. 46 ashaving ten acoustic transducers 4620, the number of acoustic transducers4620 may be greater or less than ten. In some embodiments, using highernumbers of acoustic transducers 4620 may increase the amount of audioinformation collected and/or the sensitivity and accuracy of the audioinformation. In contrast, using a lower number of acoustic transducers4620 may decrease the computing power required by an associatedcontroller 4650 to process the collected audio information. In addition,the position of each acoustic transducer 4620 of the microphone arraymay vary. For example, the position of an acoustic transducer 4620 mayinclude a defined position on the user, a defined coordinate on frame4610, an orientation associated with each acoustic transducer 4620, orsome combination thereof.

Acoustic transducers 4620(A) and 4620(B) may be positioned on differentparts of the user's ear, such as behind the pinna or within the auricleor fossa. Or, there may be additional acoustic transducers 4620 on orsurrounding the ear in addition to acoustic transducers 4620 inside theear canal. Having an acoustic transducer 4620 positioned next to an earcanal of a user may enable the microphone array to collect informationon how sounds arrive at the ear canal. By positioning at least two ofacoustic transducers 4620 on either side of a user's head (e.g., asbinaural microphones), augmented-reality device 4600 may simulatebinaural hearing and capture a 3D stereo sound field around about auser's head. In some embodiments, acoustic transducers 4620(A) and4620(B) may be connected to augmented-reality system 4600 via a wiredconnection 4630, and in other embodiments, acoustic transducers 4620(A)and 4620(B) may be connected to augmented-reality system 4600 via awireless connection (e.g., a Bluetooth connection). In still otherembodiments, acoustic transducers 4620(A) and 4620(B) may not be used atall in conjunction with augmented-reality system 4600.

Acoustic transducers 4620 on frame 4610 may be positioned along thelength of the temples, across the bridge, above or below display devices4615(A) and 4615(B), or some combination thereof. Acoustic transducers4620 may be oriented such that the microphone array is able to detectsounds in a wide range of directions surrounding the user wearing theaugmented-reality system 4600. In some embodiments, an optimizationprocess may be performed during manufacturing of augmented-realitysystem 4600 to determine relative positioning of each acoustictransducer 4620 in the microphone array.

In some examples, augmented-reality system 4600 may include or beconnected to an external device (e.g., a paired device), such asneckband 4605. Neckband 4605 generally represents any type or form ofpaired device. Thus, the following discussion of neckband 4605 may alsoapply to various other paired devices, such as charging cases, smartwatches, smart phones, wrist bands, other wearable devices, hand-heldcontrollers, tablet computers, laptop computers and other externalcompute devices, etc.

As shown, neckband 4605 may be coupled to eyewear device 4602 via one ormore connectors. The connectors may be wired or wireless and may includeelectrical and/or non-electrical (e.g., structural) components. In somecases, eyewear device 4602 and neckband 4605 may operate independentlywithout any wired or wireless connection between them. While FIG. 46illustrates the components of eyewear device 4602 and neckband 4605 inexample locations on eyewear device 4602 and neckband 4605, thecomponents may be located elsewhere and/or distributed differently oneyewear device 4602 and/or neckband 4605. In some embodiments, thecomponents of eyewear device 4602 and neckband 4605 may be located onone or more additional peripheral devices paired with eyewear device4602, neckband 4605, or some combination thereof.

Pairing external devices, such as neckband 4605, with augmented-realityeyewear devices may enable the eyewear devices to achieve the formfactor of a pair of glasses while still providing sufficient battery andcomputation power for expanded capabilities. Some or all of the batterypower, computational resources, and/or additional features ofaugmented-reality system 4600 may be provided by a paired device orshared between a paired device and an eyewear device, thus reducing theweight, heat profile, and form factor of the eyewear device overallwhile still retaining desired functionality. For example, neckband 4605may allow components that would otherwise be included on an eyeweardevice to be included in neckband 4605 since users may tolerate aheavier weight load on their shoulders than they would tolerate on theirheads. Neckband 4605 may also have a larger surface area over which todiffuse and disperse heat to the ambient environment. Thus, neckband4605 may allow for greater battery and computation capacity than mightotherwise have been possible on a stand-alone eyewear device. Sinceweight carried in neckband 4605 may be less invasive to a user thanweight carried in eyewear device 4602, a user may tolerate wearing alighter eyewear device and carrying or wearing the paired device forgreater lengths of time than a user would tolerate wearing a heavystandalone eyewear device, thereby enabling users to more fullyincorporate artificial-reality environments into their day-to-dayactivities.

Neckband 4605 may be communicatively coupled with eyewear device 4602and/or to other devices. These other devices may provide certainfunctions (e.g., tracking, localizing, depth mapping, processing,storage, etc.) to augmented-reality system 4600. In the embodiment ofFIG. 46 , neckband 4605 may include two acoustic transducers (e.g.,4620(I) and 4620(J)) that are part of the microphone array (orpotentially form their own microphone subarray). Neckband 4605 may alsoinclude a controller 4625 and a power source 4635.

Acoustic transducers 4620(I) and 4620(J) of neckband 4605 may beconfigured to detect sound and convert the detected sound into anelectronic format (analog or digital). In the embodiment of FIG. 46 ,acoustic transducers 4620(I) and 4620(J) may be positioned on neckband4605, thereby increasing the distance between the neckband acoustictransducers 4620(I) and 4620(J) and other acoustic transducers 4620positioned on eyewear device 4602. In some cases, increasing thedistance between acoustic transducers 4620 of the microphone array mayimprove the accuracy of beamforming performed via the microphone array.For example, if a sound is detected by acoustic transducers 4620(C) and4620(D) and the distance between acoustic transducers 4620(C) and4620(D) is greater than, e.g., the distance between acoustic transducers4620(D) and 4620(E), the determined source location of the detectedsound may be more accurate than if the sound had been detected byacoustic transducers 4620(D) and 4620(E).

Controller 4625 of neckband 4605 may process information generated bythe sensors on neckband 4605 and/or augmented-reality system 4600. Forexample, controller 4625 may process information from the microphonearray that describes sounds detected by the microphone array. For eachdetected sound, controller 4625 may perform a direction-of-arrival (DOA)estimation to estimate a direction from which the detected sound arrivedat the microphone array. As the microphone array detects sounds,controller 4625 may populate an audio data set with the information. Inembodiments in which augmented-reality system 4600 includes an inertialmeasurement unit, controller 4625 may compute all inertial and spatialcalculations from the IMU located on eyewear device 4602. A connectormay convey information between augmented-reality system 4600 andneckband 4605 and between augmented-reality system 4600 and controller4625. The information may be in the form of optical data, electricaldata, wireless data, or any other transmittable data form. Moving theprocessing of information generated by augmented-reality system 4600 toneckband 4605 may reduce weight and heat in eyewear device 4602, makingit more comfortable to the user.

Power source 4635 in neckband 4605 may provide power to eyewear device4602 and/or to neckband 4605. Power source 4635 may include, withoutlimitation, lithium ion batteries, lithium-polymer batteries, primarylithium batteries, alkaline batteries, or any other form of powerstorage. In some cases, power source 4635 may be a wired power source.Including power source 4635 on neckband 4605 instead of on eyeweardevice 4602 may help better distribute the weight and heat generated bypower source 4635.

FIG. 47 is an illustration of a head-mounted display device 4700according to some embodiments. The depicted embodiment includes a rightnear-eye display 4702A and a left near-eye display 4702B, which arecollectively referred to as near-eye displays 4702. Near-eye displays4702 may be transparent or semi-transparent lenses that include orutilize a display system (e.g., a projection display system) to presentmedia to a user. Examples of media presented by near-eye displays 4702include one or more images, a series of images (e.g., a video), audio,or some combination thereof. Near-eye displays 4702 may be configured tooperate as an augmented-reality near-eye display, such that a user cansee media projected by near-eye displays 4702 and see the real-worldenvironment through near-eye displays 4702. However, in someembodiments, near-eye displays 4702 may be modified to also operate asvirtual-reality near-eye displays, mixed-reality near-eye displays, orsome combination thereof. Accordingly, in some embodiments, near-eyedisplays 4702 may augment views of a physical, real-world environmentwith computer-generated elements (e.g., images, video, sound, etc.).

As shown in FIG. 47 , head-mounted display device 4700 may include asupport or frame 4704 that secures near-eye displays 4702 in place onthe head of a user, in embodiments in which near-eye displays 4702includes separate left and right displays. In some embodiments, frame4704 may be a frame of eye-wear glasses. Frame 4704 may include temples4706 configured to rest on the top of and/or behind a user's ears, abridge 4708 configured to rest on the top on the bridge of the user'snose, and rims 4710 sized and configured to rest on or against theuser's cheeks. In various embodiments, any or all of the components offrame 4704 may include or integrate the curved batteries disclosedherein. Although not illustrated in FIG. 47 , in some embodiments,head-mounted display device 4700 may include nose pads for resting onthe bridge of the user's nose. Head-mounted-display device 4700 mayadditionally or alternatively include various other features and/orcomponents, including, for example, directional speakers to provideaudio to a user, bone conduction transducers for providing sound signalsto a user via vibrational bone conduction in an auditory region of theuser's head, tracking and/or recording cameras, passive and/or activefront and/or rear facing cameras to capture images from the user'senvironment, eye tracking cameras, ambient light, night vision, and/orthermal imaging sensors, multimode connectivity antennas for wirelesscommunication, audio microphones for capturing sound in the user'senvironment, lights for illuminating a user's environment, inertial,haptic, environmental, and/or health monitoring sensors, and/or anyother suitable components, without limitation.

As noted, some artificial-reality systems may, instead of blending anartificial reality with actual reality, substantially replace one ormore of a user's sensory perceptions of the real world with a virtualexperience. One example of this type of system is a head-worn displaysystem, such as virtual-reality system 4800 in FIG. 48 , that mostly orcompletely covers a user's field of view. Virtual-reality system 4800may include a front rigid body 4802 and a band 4804 shaped to fit arounda user's head. Virtual-reality system 4800 may also include output audiotransducers 4806(A) and 4806(B). Furthermore, while not shown in FIG. 48, front rigid body 4802 may include one or more electronic elements,including one or more electronic displays, one or more inertialmeasurement units (IMUS), one or more tracking emitters or detectors,and/or any other suitable device or system for creating an artificialreality experience.

Artificial-reality systems may include a variety of types of visualfeedback mechanisms. For example, display devices in augmented-realitysystem 4600 and/or virtual-reality system 4800 may include one or moreliquid crystal displays (LCDs), light emitting diode (LED) displays,organic LED (OLED) displays digital light project (DLP) micro-displays,liquid crystal on silicon (LCoS) micro-displays, and/or any othersuitable type of display screen. Artificial-reality systems may includea single display screen for both eyes or may provide a display screenfor each eye, which may allow for additional flexibility for varifocaladjustments or for correcting a user's refractive error. Someartificial-reality systems may also include optical subsystems havingone or more lenses (e.g., conventional concave or convex lenses, Fresnellenses, adjustable liquid lenses, etc.) through which a user may view adisplay screen. These optical subsystems may serve a variety ofpurposes, including to collimate (e.g., make an object appear at agreater distance than its physical distance), to magnify (e.g., make anobject appear larger than its actual size), and/or to relay (to, e.g.,the viewer's eyes) light. These optical subsystems may be used in anon-pupil-forming architecture (such as a single lens configuration thatdirectly collimates light but results in so-called pincushiondistortion) and/or a pupil-forming architecture (such as a multi-lensconfiguration that produces so-called barrel distortion to nullifypincushion distortion).

In addition to or instead of using display screens, someartificial-reality systems may include one or more projection systems.For example, display devices in augmented-reality system 4600 and/orvirtual-reality system 4800 may include micro-LED projectors thatproject light (using, e.g., a waveguide) into display devices, such asclear combiner lenses that allow ambient light to pass through. Thedisplay devices may refract the projected light toward a user's pupiland may enable a user to simultaneously view both artificial-realitycontent and the real world. The display devices may accomplish thisusing any of a variety of different optical components, includingwaveguides components (e.g., holographic, planar, diffractive,polarized, and/or reflective waveguide elements), light-manipulationsurfaces and elements (such as diffractive, reflective, and refractiveelements and gratings), coupling elements, etc. Artificial-realitysystems may also be configured with any other suitable type or form ofimage projection system, such as retinal projectors used in virtualretina displays.

Artificial-reality systems may also include various types of computervision components and subsystems. For example, augmented-reality system4500, augmented-reality system 4600, and/or virtual-reality system 4800may include one or more optical sensors, such as two-dimensional (2D) or3D cameras, time-of-flight depth sensors, single-beam or sweeping laserrangefinders, 3D LiDAR sensors, and/or any other suitable type or formof optical sensor. An artificial-reality system may process data fromone or more of these sensors to identify a location of a user, to mapthe real world, to provide a user with context about real-worldsurroundings, and/or to perform a variety of other functions.

Artificial-reality systems may also include one or more input and/oroutput audio transducers. In the examples shown in FIGS. 45 and 48 ,output audio transducers 4508(A), 4508(B), 4806(A), and 4806(B) mayinclude voice coil speakers, ribbon speakers, electrostatic speakers,piezoelectric speakers, bone conduction transducers, cartilageconduction transducers, and/or any other suitable type or form of audiotransducer. Similarly, input audio transducers 4510 may includecondenser microphones, dynamic microphones, ribbon microphones, and/orany other type or form of input transducer. In some embodiments, asingle transducer may be used for both audio input and audio output.

While not shown in FIGS. 45-48 , artificial-reality systems may includetactile (i.e., haptic) feedback systems, which may be incorporated intoheadwear, gloves, body suits, handheld controllers, environmentaldevices (e.g., chairs, floormats, etc.), and/or any other type of deviceor system. Haptic feedback systems may provide various types ofcutaneous feedback, including vibration, force, traction, texture,and/or temperature. Haptic feedback systems may also provide varioustypes of kinesthetic feedback, such as motion and compliance. Hapticfeedback may be implemented using motors, piezoelectric actuators,fluidic systems, and/or a variety of other types of feedback mechanisms.Haptic feedback systems may be implemented independent of otherartificial-reality devices, within other artificial-reality devices,and/or in conjunction with other artificial-reality devices.

By providing haptic sensations, audible content, and/or visual content,artificial-reality systems may create an entire virtual experience orenhance a user's real-world experience in a variety of contexts andenvironments. For instance, artificial-reality systems may assist orextend a user's perception, memory, or cognition within a particularenvironment. Some systems may enhance a user's interactions with otherpeople in the real world or may enable more immersive interactions withother people in a virtual world. Artificial-reality systems may also beused for educational purposes (e.g., for teaching or training inschools, hospitals, government organizations, military organizations,business enterprises, etc.), entertainment purposes (e.g., for playingvideo games, listening to music, watching video content, etc.), and/orfor accessibility purposes (e.g., as hearing aids, visuals aids, etc.).The embodiments disclosed herein may enable or enhance a user'sartificial-reality experience in one or more of these contexts andenvironments and/or in other contexts and environments.

As noted, artificial-reality systems 4500, 4600, and 4800 may be usedwith a variety of other types of devices to provide a more compellingartificial-reality experience. These devices may be haptic interfaceswith transducers that provide haptic feedback and/or that collect hapticinformation about a user's interaction with an environment. Theartificial-reality systems disclosed herein may include various types ofhaptic interfaces that detect or convey various types of hapticinformation, including tactile feedback (e.g., feedback that a userdetects via nerves in the skin, which may also be referred to ascutaneous feedback) and/or kinesthetic feedback (e.g., feedback that auser detects via receptors located in muscles, joints, and/or tendons).

Haptic feedback may be provided by interfaces positioned within a user'senvironment (e.g., chairs, tables, floors, etc.) and/or interfaces onarticles that may be worn or carried by a user (e.g., gloves,wristbands, etc.). As an example, FIG. 49 illustrates a vibrotactilesystem 4900 in the form of a wearable glove (haptic device 4910) andwristband (haptic device 4920). Haptic device 4910 and haptic device4920 are shown as examples of wearable devices that include a flexible,wearable textile material 4930 that is shaped and configured forpositioning against a user's hand and wrist, respectively. Thisdisclosure also includes vibrotactile systems that may be shaped andconfigured for positioning against other human body parts, such as afinger, an arm, a head, a torso, a foot, or a leg. By way of example andnot limitation, vibrotactile systems according to various embodiments ofthe present disclosure may also be in the form of a glove, a headband,an armband, a sleeve, a head covering, a sock, a shirt, or pants, amongother possibilities. In some examples, the term “textile” may includeany flexible, wearable material, including woven fabric, non-wovenfabric, leather, cloth, a flexible polymer material, compositematerials, etc.

One or more vibrotactile devices 4940 may be positioned at leastpartially within one or more corresponding pockets formed in textilematerial 4930 of vibrotactile system 4900. Vibrotactile devices 4940 maybe positioned in locations to provide a vibrating sensation (e.g.,haptic feedback) to a user of vibrotactile system 4900. For example,vibrotactile devices 4940 may be positioned against the user'sfinger(s), thumb, or wrist, as shown in FIG. 49 . Vibrotactile devices4940 may, in some examples, be sufficiently flexible to conform to orbend with the user's corresponding body part(s).

A power source 4950 (e.g., a battery) for applying a voltage to thevibrotactile devices 4940 for activation thereof may be electricallycoupled to vibrotactile devices 4940, such as via conductive wiring4952. In some examples, each of vibrotactile devices 4940 may beindependently electrically coupled to power source 4950 for individualactivation. In some embodiments, a processor 4960 may be operativelycoupled to power source 4950 and configured (e.g., programmed) tocontrol activation of vibrotactile devices 4940.

Vibrotactile system 4900 may be implemented in a variety of ways. Insome examples, vibrotactile system 4900 may be a standalone system withintegral subsystems and components for operation independent of otherdevices and systems. As another example, vibrotactile system 4900 may beconfigured for interaction with another device or system 4970. Forexample, vibrotactile system 4900 may, in some examples, include acommunications interface 4980 for receiving and/or sending signals tothe other device or system 4970. The other device or system 4970 may bea mobile device, a gaming console, an artificial-reality (e.g.,virtual-reality, augmented-reality, mixed-reality) device, a personalcomputer, a tablet computer, a network device (e.g., a modem, a router,etc.), a handheld controller, etc. Communications interface 4980 mayenable communications between vibrotactile system 4900 and the otherdevice or system 4970 via a wireless (e.g., Wi-Fi, Bluetooth, cellular,radio, etc.) link or a wired link. If present, communications interface4980 may be in communication with processor 4960, such as to provide asignal to processor 4960 to activate or deactivate one or more of thevibrotactile devices 4940.

Vibrotactile system 4900 may optionally include other subsystems andcomponents, such as touch-sensitive pads 4990, pressure sensors, motionsensors, position sensors, lighting elements, and/or user interfaceelements (e.g., an on/off button, a vibration control element, etc.).During use, vibrotactile devices 4940 may be configured to be activatedfor a variety of different reasons, such as in response to the user'sinteraction with user interface elements, a signal from the motion orposition sensors, a signal from the touch-sensitive pads 4990, a signalfrom the pressure sensors, a signal from the other device or system4970, etc.

Although power source 4950, processor 4960, and communications interface4980 are illustrated in FIG. 49 as being positioned in haptic device4920, the present disclosure is not so limited. For example, one or moreof power source 4950, processor 4960, or communications interface 4980may be positioned within haptic device 4910 or within another wearabletextile.

Haptic wearables, such as those shown in and described in connectionwith FIG. 49 , may be implemented in a variety of types ofartificial-reality systems and environments. FIG. 50 shows an exampleartificial-reality environment 5000 including one head-mountedvirtual-reality display and two haptic devices (i.e., gloves), and inother embodiments any number and/or combination of these components andother components may be included in an artificial-reality system. Forexample, in some embodiments there may be multiple head-mounted displayseach having an associated haptic device, with each head-mounted displayand each haptic device communicating with the same console, portablecomputing device, or other computing system.

Head-mounted display 5002 generally represents any type or form ofvirtual-reality system, such as virtual-reality system 4800 in FIG. 48 .Haptic device 5004 generally represents any type or form of wearabledevice, worn by a user of an artificial-reality system, that provideshaptic feedback to the user to give the user the perception that he orshe is physically engaging with a virtual object. In some embodiments,haptic device 5004 may provide haptic feedback by applying vibration,motion, and/or force to the user. For example, haptic device 5004 maylimit or augment a user's movement. To give a specific example, hapticdevice 5004 may limit a user's hand from moving forward so that the userhas the perception that his or her hand has come in physical contactwith a virtual wall. In this specific example, one or more actuatorswithin the haptic advice may achieve the physical-movement restrictionby pumping fluid into an inflatable bladder of the haptic device. Insome examples, a user may also use haptic device 5004 to send actionrequests to a console. Examples of action requests include, withoutlimitation, requests to start an application and/or end the applicationand/or requests to perform a particular action within the application.

While haptic interfaces may be used with virtual-reality systems, asshown in FIG. 50 , haptic interfaces may also be used withaugmented-reality systems, as shown in FIG. 51 . FIG. 51 is aperspective view of a user 5110 interacting with an augmented-realitysystem 5100. In this example, user 5110 may wear a pair ofaugmented-reality glasses 5120 that may have one or more displays 5122and that are paired with a haptic device 5130. In this example, hapticdevice 5130 may be a wristband that includes a plurality of bandelements 5132 and a tensioning mechanism 5134 that connects bandelements 5132 to one another.

One or more of band elements 5132 may include any type or form ofactuator suitable for providing haptic feedback. For example, one ormore of band elements 5132 may be configured to provide one or more ofvarious types of cutaneous feedback, including vibration, force,traction, texture, and/or temperature. To provide such feedback, bandelements 5132 may include one or more of various types of actuators. Inone example, each of band elements 5132 may include a vibrotactor (e.g.,a vibrotactile actuator) configured to vibrate in unison orindependently to provide one or more of various types of hapticsensations to a user. Alternatively, only a single band element or asubset of band elements may include vibrotactors.

Haptic devices 4910, 4920, 5004, and 5130 may include any suitablenumber and/or type of haptic transducer, sensor, and/or feedbackmechanism. For example, haptic devices 4910, 4920, 5004, and 5130 mayinclude one or more mechanical transducers, piezoelectric transducers,and/or fluidic transducers. Haptic devices 4910, 4920, 5004, and 5130may also include various combinations of different types and forms oftransducers that work together or independently to enhance a user'sartificial-reality experience. In one example, each of band elements5132 of haptic device 5130 may include a vibrotactor (e.g., avibrotactile actuator) configured to vibrate in unison or independentlyto provide one or more of various types of haptic sensations to a user.

The process parameters and sequence of the steps described and/orillustrated herein are given by way of example only and can be varied asdesired. For example, while the steps illustrated and/or describedherein may be shown or discussed in a particular order, these steps donot necessarily need to be performed in the order illustrated ordiscussed. The various exemplary methods described and/or illustratedherein may also omit one or more of the steps described or illustratedherein or include additional steps in addition to those disclosed.

The preceding description has been provided to enable others skilled inthe art to best utilize various aspects of the exemplary embodimentsdisclosed herein. This exemplary description is not intended to beexhaustive or to be limited to any precise form disclosed. Manymodifications and variations are possible without departing from thespirit and scope of the present disclosure. The embodiments disclosedherein should be considered in all respects illustrative and notrestrictive.

Unless otherwise noted, the terms “connected to” and “coupled to” (andtheir derivatives), as used in the specification, are to be construed aspermitting both direct and indirect (i.e., via other elements orcomponents) connection. In addition, the terms “a” or “an,” as used inthe specification, are to be construed as meaning “at least one of.”Finally, for ease of use, the terms “including” and “having” (and theirderivatives), as used in the specification, are interchangeable with andhave the same meaning as the word “comprising.”

What is claimed is:
 1. A wearable battery-pack accessory comprising: oneor more curved batteries; charging circuitry that charges the one ormore curved batteries; supplying circuitry that supplies power to aconnected external computing device; and an outer housing comprising atleast: a first curved surface oriented to face away from a user when thewearable battery-pack accessory is worn by the user; and a second curvedsurface oriented to face towards the user when the wearable battery-packaccessory is worn by the user, the second curved surface having avarying radius of curvature derived by: measuring body contours of aplurality of individuals; and constructing a model of a body based atleast in part on an averaging of the body contours of the plurality ofindividuals, wherein: the model of the body comprises one or more splinecurves; and the varying radius of curvature of the second curved surfacesubstantially matches a varying radius of curvature of the one or morespline curves of the model of the body.
 2. The wearable battery-packaccessory of claim 1, wherein the connected external computing devicecomprises a head-mounted display system.
 3. The wearable battery-packaccessory of claim 2, wherein the one or more curved batteries comprise:a top battery having a first spline surface curved to conform to a topside of the user's head; a right battery having a second spline surfacecurved to conform to a right side of the user's head; or a left batteryhaving a third spline surface curved to conform to a left side of theuser's head.
 4. The wearable battery-pack accessory of claim 1, wherein:the first curved surface of the outer housing has: a first radius ofcurvature at a first point; and a second radius of curvature at a secondpoint; the first radius of curvature differs from the second radius ofcurvature; the second curved surface of the outer housing has: a thirdradius of curvature at a third point; and a fourth radius of curvatureat a fourth point; and the third radius of curvature differs from thefourth radius of curvature.
 5. The wearable battery-pack accessory ofclaim 1, wherein each of the one or more curved batteries has an innerradius between 80 millimeters and 95 millimeters.
 6. The wearablebattery-pack accessory of claim 1, wherein each of the one or morecurved batteries has an inner radius between 70 millimeters and 125millimeters.
 7. The wearable battery-pack accessory of claim 1, furthercomprising: an input port for receiving power from an external powersource; and an output port for transmitting power to the connectedexternal computing device, wherein the charging circuitry charges theone or more curved batteries using power from the external power sourcewhile the supplying circuitry supplies power to the connected externalcomputing device.
 8. The wearable battery-pack accessory of claim 1,further comprising an input/output port for receiving power from anexternal power source and transmitting power to the connected externalcomputing device, wherein: the charging circuitry charges the one ormore curved batteries when the external power source is connected to theinput/output port; and the supplying circuitry supplies power to theconnected external computing device when the connected externalcomputing device is connected to the input/output port.
 9. Ahead-mounted display system comprising: a head-mounted display; a strapthat is coupled to the head-mounted display and wraps around the back ofa user's head when the user is wearing the head-mounted display; and abattery-pack accessory detachably coupled to the strap, the battery-packaccessory comprising: one or more curved batteries; charging circuitrythat charges the one or more curved batteries; supplying circuitry thatsupplies power to the head-mounted display; and an outer housingcomprising at least: a first curved surface oriented to face away fromthe user when the battery-pack accessory is worn by the user; and asecond curved surface oriented to face towards the user when thebattery-pack accessory is worn by the user, the second curved surfacehaving a varying radius of curvature derived by: measuring head contoursof a plurality of individuals; and constructing a model of a head basedat least in part on an averaging of the head contours of the pluralityof individuals, wherein: the model of the head comprises one or morespline curves; and the varying radius of curvature of the second curvedsurface substantially matches a varying radius of curvature of the oneor more spline curves of the model of the head.
 10. The head-mounteddisplay system of claim 9, wherein: the strap comprises an adjustmentmechanism for adjusting a size of the strap; the adjustment mechanismcomprises a dial; the outer housing of the battery-pack accessorycomprises a notch that exposes the dial when the battery-pack accessoryis coupled to the strap.
 11. The head-mounted display system of claim 9,wherein the outer housing of the battery-pack accessory comprises aninterface for coupling the battery-pack accessory, via a friction fit,to the strap of the head-mounted display system.
 12. The head-mounteddisplay system of claim 9, wherein: the one or more curved batteriescomprise: a top battery curved to conform to a top side of the user'shead; a right battery curved to conform to a right side of the user'shead; or a left battery curved to conform to a left side of the user'shead; and at least one of the one or more curved batteries has a varyingradius of curvature.
 13. The head-mounted display system of claim 9,wherein each of the one or more curved batteries has an inner radiusbetween 80 millimeters and 95 millimeters.
 14. The head-mounted displaysystem of claim 9, wherein each of the one or more curved batteries hasan inner radius between 70 millimeters and 125 millimeters.
 15. Thehead-mounted display system of claim 9, wherein the battery-packaccessory further comprises: an input port for receiving power from anexternal power source; and an output port for transmitting power to thehead-mounted display, wherein the charging circuitry charges the one ormore curved batteries using power from the external power source whilethe supplying circuitry supplies power to the head-mounted display. 16.A method comprising: measuring body contours of a plurality ofindividuals; constructing a model of a body based at least in part on anaveraging of the body contours of the plurality of individuals, whereinthe model of the body comprises one or more spline curves; providing acurved battery; coupling the curved battery to charging circuitry thatcharges the curved battery; coupling the curved battery to supplyingcircuitry that supplies power to an external computing device; andplacing the curved battery, the charging circuitry, and the supplyingcircuitry within an outer housing of a battery-pack accessory, the outerhousing comprising at least: a first curved surface oriented to faceaway from a user when the battery-pack accessory is worn by the user;and a second curved surface oriented to face towards the user when thebattery-pack accessory is worn by the user, the second curved surfacehaving a varying radius of curvature substantially matching a varyingradius of curvature of the one or more spline curves of the model of thebody.
 17. The method of claim 16, wherein providing the curved batterycomprises: placing a flat electrode assembly of the curved batterybetween spline surfaces of an upper jig and a lower jig; curving theflat electrode assembly by pressing the flat electrode assembly betweenthe spline surfaces of the upper jig and the lower jig; separating theupper jig from the lower jig; and removing the curved electrode assemblyfrom the upper jig and the lower jig.
 18. The wearable battery-packaccessory of claim 1, wherein: the one or more spline curves of themodel of the body are defined by at least: a starting point; an endingpoint; a midpoint; a first radius at the starting point; a second radiusat the ending point; and a third radius at the midpoint; and the firstradius, the second radius, and the third radius are different.
 19. Thewearable battery-pack accessory of claim 1, wherein the one or morespline curves of the model of the body are defined by at least: a firstcurve segment having a continuously varying radius of curvature; and asecond curve segment having a constant radius of curvature.
 20. Thewearable battery-pack accessory of claim 1, wherein the one or morespline curves of the model of the body are defined by multiple controlpoints.